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Gerard Trottet   Submitted: 2007-12-27 20:24

Radio observations at 210 GHz taken by the BErnese Multibeam RAdiometer for KOSMA (BEMRAK) are combined with hard X-ray and gamma-ray observations from the SONG instrument onboard CORONA-F and the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) to investigate high energy particle acceleration during the energetic solar flare of 2003 October 28. Two distinct components at submillimeter wavelengths are found. The first is a gradual, long-lasting (>30 min) component with large apparent source sizes (~60 arcsec). Its spectrum below ~200 GHz is consistent with synchrotron emission from flare-accelerated electrons producing hard X-ray and gamma-ray bremsstrahlung assuming a magnetic field strength of >200 G in the radio source and a confinement time of the radio-emitting electrons in the source of less than 30 s. At even higher frequencies, the spectrum deviates from synchrotron emission and is increasing with frequency, as also seen in other large flares, but the interpretation is unclear. The other component is impulsive and starts simultaneously with high energy (>200 MeV/nucleon) proton acceleration and the production of pions. The derived radio source size is compact (<10 arcsec) and, within the uncertainties, the emission is co-spatial with the location of precipitating flare-accelerated >30 MeV protons as seen in Gamma-ray imaging of the 2.2 MeV line emission. The close correlation in time and space of radio emission with the production of pions suggests that synchrotron emission of positrons produced in charged-pion decay might be responsible for the observed compact radio source. However, order-of-magnitude approximations rather suggest that the derived numbers of positrons from charged-pion decay are probably too small compared to what is needed to produce the observed radio emission. Synchrotron emission from energetic electrons therefore appears as the most likely emission mechanism for the compact radio source seen in the impulsive phase although it does not account for its close correlation, in time and space, with pion production.

Authors: G. Trottet, S. Krucker, T. Luthi, A. Magun
Projects: CORONAS-F/SPIRIT,RHESSI,TRACE

Publication Status: in press, ApJ
Last Modified: 2007-12-28 09:20
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Subject will be restored when possible  

Gerard Trottet   Submitted: 2007-12-27 20:22

Radio observations at 210 GHz taken by the BErnese Multibeam RAdiometer for KOSMA (BEMRAK) are combined with hard X-ray and gamma-ray observations from the SONG instrument onboard CORONA-F and the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) to investigate high energy particle acceleration during the energetic solar flare of 2003 October 28. Two distinct components at submillimeter wavelengths are found. The first is a gradual, long-lasting (>30 min) component with large apparent source sizes (~60 arcsec). Its spectrum below ~200 GHz is consistent with synchrotron emission from flare-accelerated electrons producing hard X-ray and gamma-ray bremsstrahlung assuming a magnetic field strength of >200 G in the radio source and a confinement time of the radio-emitting electrons in the source of less than 30 s. At even higher frequencies, the spectrum deviates from synchrotron emission and is increasing with frequency, as also seen in other large flares, but the interpretation is unclear. The other component is impulsive and starts simultaneously with high energy (>200 MeV/nucleon) proton acceleration and the production of pions. The derived radio source size is compact (<10 arcsec) and, within the uncertainties, the emission is co-spatial with the location of precipitating flare-accelerated >30 MeV protons as seen in Gamma-ray imaging of the 2.2 MeV line emission. The close correlation in time and space of radio emission with the production of pions suggests that synchrotron emission of positrons produced in charged-pion decay might be responsible for the observed compact radio source. However, order-of-magnitude approximations rather suggest that the derived numbers of positrons from charged-pion decay are probably too small compared to what is needed to produce the observed radio emission. Synchrotron emission from energetic electrons therefore appears as the most likely emission mechanism for the compact radio source seen in the impulsive phase although it does not account for its close correlation, in time and space, with pion production.

Authors: G. Trottet, S. Krucker, T. Luthi, A. Magun
Projects: CORONAS-F/SPIRIT,RHESSI,TRACE

Publication Status: in press
Last Modified: 2007-12-27 20:22
Go to main E-Print page  Edit Entry  Download Preprint  Delete Entry 


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